"Every winter, respiratory diseases cause significant sickness and put pressure on healthcare systems, but the exact timing and mix of viruses can vary a lot from one year to another. Having an up-to-date picture of epidemic trends can help public health systems plan for periods of high healthcare demand. But it can be difficult to separate the signal from the noise in raw data, which is where the mathematical and statistical models described in this study can help.

"Using these models and the latest disease surveillance data, researchers from New Zealand and Australia provide weekly updates to the Public Health Agency and Te Whatu Ora, as well as public health partners across the Tasman. These contain an analysis of the latest trends and a forecast for the next few weeks.

"Last year saw unusually high levels of influenza through the spring and early summer, due to the novel 'subclade K' of H3N2 influenza. This may be the reason that this winter's flu wave has started later than usual, with low levels through June and July followed by a rapid recent increase. This winter's RSV season has been fairly average in size and timing. Covid-19, which has not yet developed a clear seasonal pattern, has remained at very low levels so far this winter.

"Because of the late start to the influenza season, it is still not too late to get a flu jab if you haven't already had one this year."